Companies have long known the benefits of making sure their workers get a good night's sleep--and they would be wise to let their PCs do the same, Microsoft says. With Windows Vista, Microsoft plans to <A HREF="http://news.zdnet.com/2100-3513_22-6126287.html?tag=nl.e589">put machines to sleep</A> after an hour of inactivity. While businesses and consumers can change that setting, the software maker said that they would be smart to let their computers nod off. Microsoft estimates that allowing a PC to go to sleep during off hours, as compared with leaving it on all the time, saves anywhere from $55 a year to $70 annually, depending on the type of monitor.